The present invention relates to a muffler, and more particularly to a straight through type muffler for generating an exhaust flow from an internal combustion engine.
In order to reduce the noise of the combustion and exhaust of an internal combustion engine, exhaust gases from the engine are passed through a muffler. For an automotive vehicle, the muffler is interdisposed between an exhaust pipe and a tailpipe. Referring to FIG. 1, a conventional steel muffler for use in an automotive vehicle includes four resonance chambers in which the gases are expanded slowly, and four parallel porous ducts each of which is used to communicate with two of the resonance chambers at both ends thereof. The ducts form four flow-reversing bends to provide adequate noise control.
However, it is understood that there is a relatively large back pressure developed from this type of muffler. The back pressure prevents free flow of the exhaust gases from the engine and, as a result, not all of the burned gases will be exhausted from the cylinders. Such unexpelled gases dilute the incoming combustion gases so that engine power is reduced. In order to reduce the loss of the engine power, the mufflers are excluded from racing cars.
As is well known in the art, a straight through type muffler is used to reduce the loss of the engine power. Although the exhaust flow within the straight through type muffler is more smooth, its structure used for attenuating noise is only a blanket of sound-absorbing material lining the interior walls of a duct. The noise attenuating effect of the conventional straight through type muffler is not satisfactory.